Different means are known to enhance the production speed of electrical cables. The production speed is significantly dependent on how efficiently the insulation layer(s) of the extruded cable can be heated to the temperature necessary for the crosslinking reaction. The main limiting factor of the heating is the low heat conduction rate inside the insulation. Therefore different arrangements have been used to speed up the heating rate of the insulation layer. These arrangements comprise preheaters for heating the electrical conductor to a temperature above the ambient temperature prior to entering the extrusion head of the production line for heating the insulation layer also from the inside. However, this preheating is limited because of, for instance, copper oxidation, conductor tape deformation and moisture-block material degradation. Also radiant heat sources have been used, but the maximum admissible temperature of the outer surface of the extruded cable limits the utilisation of these radiant heat sources. Furthermore, inductive post-heaters are used for this heating purpose after the extrusion of the insulation layer of the cable.